Single-Coil Motor Driver With Linear Speed Control and Low EMI
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Solution Overview
Problem
Existing motor drivers for single coil motors face challenges in speed control due to electromagnetic interference (EMI) and limitations in motor design, particularly requiring pulse width modulation (PWM) control, which restricts motor design freedom and introduces noise issues.
Innovation Solution
A motor driver system comprising a bridge driver, controller, and voltage regulators that allows for speed control without PWM by commuting motor voltage in line with rotor position, enabling control of motor voltage and current to achieve a preferred operating point, and using soft switching and sinewave shaping to reduce noise and heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If PWM control is used for motor speed control, then speed control capability is improved, but electromagnetic interference increases and motor design freedom is limited
Solution Approach 1:
The patent changes the control parameter from PWM duty cycle to direct motor voltage regulation. The voltage regulator continuously adjusts the motor voltage to match the back-EMF, eliminating the need for PWM switching. This parameter change resolves the contradiction by providing smooth speed control without the electromagnetic interference associated with PWM switching.
Solution Approach 2:
The patent replaces the electronic switching mechanism (PWM) with a voltage regulation mechanism that directly controls motor voltage. By substituting the PWM switching approach with continuous voltage regulation, the system achieves speed control without generating electromagnetic interference from rapid switching operations.
2Ease of operation
If PWM control is used for motor speed control, then speed control capability is improved, but motor design freedom is limited
Solution Approach 1:
The patent changes the control approach from PWM-based to voltage-regulation-based, which removes the minimum coil inductance requirement. This allows motor designers to use lower inductance values and different motor topologies without being constrained by PWM switching requirements, thereby improving motor design freedom while maintaining speed control capability.
3Object-generated harmful factors
If linear voltage regulation is used instead of PWM, then electromagnetic interference is reduced, but heat dissipation increases
Solution Approach 1:
The patent implements dynamic voltage regulation where the regulator continuously adjusts the motor voltage to match the back-EMF. This dynamic approach allows the system to operate in a high-efficiency region by minimizing the voltage differential across the regulator, thereby reducing heat dissipation while maintaining the low EMI benefits of linear regulation.
Solution Approach 2:
The patent uses feedback from the motor's back-EMF to regulate the output voltage. This feedback mechanism ensures that the voltage regulator only provides the necessary voltage to drive the motor at the desired speed, minimizing excess voltage drop and associated heat dissipation while maintaining electromagnetic compatibility.
4Measurement precision
If motor voltage is regulated to preferred value, then operating point control is improved, but device complexity increases
Solution Approach 1:
The patent makes the voltage regulator serve multiple functions: it regulates motor voltage to control speed, provides a stable reference voltage for the control circuitry, and eliminates the need for separate PWM generation and switching components. This multi-functionality reduces overall device complexity while maintaining precise operating point control.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides effective speed control without PWM, reduces noise and heat dissipation, and allows for flexible motor design by controlling motor voltage and current, thereby enhancing motor performance and reliability.
Implementation Method 1
a bridge driver configured for applying a driving signal to the single coil by commuting a motor voltage (Vmot), such that an induced motor current (Imot) changes direction in line with the rotor position
Implementation Method 2
a first voltage regulator configured for regulating the motor voltage, and thus the resulting motor current, to the preferred value
Data Source
AI summary
A motor driver for driving a single coil motor, the motor driver includes: a bridge driver configured for applying a driving signal to the single coil by commuting a motor voltage (Vmot) or a motor current (Imot), supplied to the bridge driver, between terminals (OUT1, OUT2) of the single coil; a controller configured for controlling the commuting of the bridge driver and for setting a preferred value of the motor voltage in function of a preferred operating point; a first voltage regulator configured for regulating the motor voltage or the motor current to the preferred value.